Numerous variations and modifications of these forms exist.
With these variations is involved the problem of the early history of the Israelites.
It is subject, however, to extreme and rapid variations in temperature, to alternations of dry and humid winds (the latter, called catias, being irritating and oppressive), to chilling night mists brought up from the coast by the westerly winds, and to other influences productive of malaria, catarrh, fevers, bilious disorders and rheumatism.
In reality, however, it experiences fewer climatic variations than the other great continents, owing to its distance (28°) from the Antarctic circle and (11°) from the equator.
To eliminate the sluggish action of the selenium transmitter a selenium cell similar to that at the transmitting station is arranged at the receiving apparatus, and exposed to precisely similar variations of light, the arrangement being such that the lag of this cell counteracts the lag of the transmitting cell.